Author:

Alexander Zinchenko(Uiniversity of Colorado, Boulder)

Microstructural evolution and temporal dynamics of the sedimentation rate
$U(t)$ are studied for a monodisperse suspension of non-Brownian spherical
particles subject to van der Waals attraction and electrostatic repulsion in
the realistic range of colloidal parameters (Hamaker constant, surface
potential, double layer thickness etc.). A novel economical high-order
multipole algorithm is used to fully resolve hydrodynamical interactions in
the dynamical simulations with up to 500 spheres in a periodic box and
O(10$^{\mathrm{6}})$ time steps, combined with geometry perturbation
(Zinchenko A.Z. Phil. Trans. R. Soc. Lond. A (1998), vol. 356, 2953-2998) to
incorporate lubrication and extend the solution to arbitrarily small
particle separations. The total colloidal force near the secondary minimum
often greatly exceeds the effective gravity/buoyancy force, resulting in the
formation of strong but flexible bonds and large clusters as the suspension
evolves from an initial well-mixed state of non-aggregated spheres. Ensemble
averaging over many initial configurations is used to predict $U(t)$ for particle
volume fractions between 0.1 and 0.25. The results are fully convergent,
system-size independent and cover a 2-2.5 fold growth of $U(t)$ after a latency
time.

To cite this abstract, use the following reference: http://meetings.aps.org/link/BAPS.2017.DFD.M36.9